氮肥水平对稻田细菌群落及N2O排放的影响

作为土壤氮素转化的驱动者,微生物群落结构关系着稻田氮素利用及温室气体N_2O排放等问题。本研究分别基于高通量测序和荧光定量PCR技术,分析了不同氮肥水平[CK(不施氮)、N(施N 180 kg·hm-2)、2/3N(施N 120 kg·hm-2)、1/3N(施N 60 kg·hm-2)]下稻田细菌群落及硝化反硝化关键微生物功能基因丰度的变化。结果显示:氮肥水平提高增加了稻田细菌物种丰富度Chao1指数和群落多样性Shannon指数,改变了细菌群落组成,其中与硝化作用相关的硝化螺菌门Nitrospirae和嗜酸的醋杆菌门Acidobacteria的相对丰度随氮肥水平提高而增加,但甲烷氧化菌Methylosinus的相对丰度随氮肥水平提高而降低。氮肥水平对稻田硝化作用关键微生物氨氧化细菌amo A基因丰度的影响较大,0~5 cm和10~20 cm深度土层中的amo A基因丰度均随氮肥用量增加而提高;反硝化作用关键微生物功能基因nir S、qno B和nos Z的丰度在不施肥处理(CK)中显著低于施肥处理(1/3N、2/3N和N)(P0.05),但1/3N、2/3N和N处理的稻田nir S基因丰度没有明显差异;0~5 cm土层中qno B和nos Z基因丰度存在随氮肥水平提高而增加的趋势,10~20 cm土层中nos Z基因丰度在2/3N和N处理下显著高于1/3N处理(P0.05)。N处理的稻田N_2O排放通量显著高于2/3N及1/3N处理(P0.05),后者又显著高于CK处理(P0.05)。相关分析结果表明稻田N_2O排放通量与0~5 cm土层中硝化螺菌门Nitrospirae相对丰度及10~20 cm土层中amo A基因丰度存在显著相关性(P0.05,n=10)。综上所述,氮肥水平提高增加了稻田细菌群落多样性,促进了稻田N_2O排放,且本研究稻田中硝化作用微生物群落及丰度变化与稻田N_2O排放的关系更为密切。     

不同生物硝化抑制剂对红壤性水稻土N2O排放的影响及其机制

为揭示不同生物硝化抑制剂(BNIs)对红壤性水稻土N₂O排放的影响差异及作用机制,通过21 d的土柱淹水培养试验,比较了三种BNIs 1,9-癸二醇(1,9-D)、亚麻酸(LN)和3-(4-羟基苯基)丙酸甲酯(MHPP)与化学合成硝化抑制剂双氰胺(DCD)对土壤N₂O排放及相关硝化、反硝化功能基因的影响。结果表明:不同BNIs(1,9-D、LN、MHPP)可以显著平均降低土壤N₂O日排放峰值40.1%;1,9-D和MHPP可分别抑制N₂O排放总量44.5%和43.9%,而DCD和LN对N₂O排放总量没有显著影响。1,9-D和MHPP对AOA(氨氧化古菌)、AOB(氨氧化细菌)硝化菌和nirS、nirK型反硝化菌的调控均有所不同,1,9-D可以同时抑制AOA、AOB和nirS微生物的生长;MHPP仅可以抑制AOA的生长;其中,AOA-amoA和nirS基因丰度与土壤N₂O的排放呈显著正相关关系。同时,1,9-D和MHPP均增加了nosZ基因丰度及其与AOA-...     

Linkage of N2O emissions to the abundance of soil ammonia oxidizers and denitrifiers in purple soil under long-term fertilization

Abstract

Microbial nitrification and denitrification are responsible for the majority of soil nitrous (N₂O) emissions. In this study, N₂O emissions were measured and the abundance of ammonium oxidizers and denitrifiers were quantified in purple soil in a long-term fertilization experiment to explore their relationships. The average N₂O fluxes and abundance of the amoAgene in ammonia-oxidizing bacteria during the observed dry season were highest when treated with mixed nitrogen, phosphorus and potassium fertilizer (NPK) and a single N treatment (N) using NH₄HCO₃as the sole N source; lower values were obtained using organic manure with pig slurry and added NPK at a ratio of 40%:60% (OMNPK),organic manure with pig slurry (OM) and returning crop straw residue plus synthetic NH₄HCO₃fertilizer at a ratio of 15%:85% (SRNPK). The lowest N₂O fluxes were observed in the treatment that used crop straw residue(SR) and in the control with no fertilizer (CK). Soil NH₄⁺provides the substrate for nitrification generating N₂O as a byproduct. The N₂O flux was significantly correlated with the abundance of the amoA gene in ammonia-oxidizing bacteria (r = 0.984, p < 0.001), which was the main driver of nitrification. During the wet season, soil nitrate (NO₃^?) and soil organic matter (SOC) were found positively correlated with N₂O emissions (r = 0.774, p = 0.041 and r = 0.827, p = 0.015, respectively). The nirS gene showed a similar trend with N₂O fluxes. These results show the relationship between the abundance of soil microbes and N₂O emissions and suggest that N₂O emissions during the dry season were due to nitrification, whereas in wet season, denitrification might dominate N₂O emission.     

Decreased nitrous oxide emissions associated with functional microbial genes under bio-organic fertilizer application in vegetable fields

Bio-organic fertilizers enriched with plant growth-promoting microbes(PGPMs)have been widely used in crop fields to promote plant growth and maintain soil microbiome functions.However,their potential effects on N₂O emissions are of increasing concern.In this study,an in situ measurement experiment was conducted to investigate the effect of organic fertilizer containing Trichoderma guizhouense(a plant growth-promoting fungus)on soil N₂O emissions from a greenhouse vegetable field.The following four treatments were used:no fertilizer(control),chemical fertilizer(NPK),organic fertilizer derived from cattle manure(O),and organic fertilizer containing T.guizhouense(O+T,referring to bio-organic fertilizer).The abundances of soil N cycling-related functional genes(amoA)from ammonium-oxidizing bacteria(AOB)and archaea(AOA),as well as nirS,nirK,and nosZ,were simultaneously determined using quantitative PCR(qPCR).Compared to the NPK plot,seasonal total N₂O emissions decreased by 11.7%and 18.7%in the O and O+T plots,respectively,which was attributed to lower NH₄⁺-N content and AOB amoA abundance in the O and O+T plots.The nosZ abundance was significantly greater in the O+T plot,whilst the AOB amoA abundance was significantly lower in the O+T plot than in the O plot.Relative to the organic fertilizer,bio-organic fertilizer application tended to decrease N₂O emissions by 7.9%and enhanced vegetable yield,resulting in a significant decrease in yield-scaled N₂O emissions.Overall,the results of this study suggested that,compared to organic and chemical fertilizers,bio-organic fertilizers containing PGPMs could benefit crop yield and mitigate N₂O emissions in vegetable fields.     

Nitrous Oxide Emission in Relation to Paddy Soil Microbial Communities in South China Under Different Irrigation and Nitrogen Strategies

Irrigation and fertilization affect soil microbial communities in relation to nitrogen transformation and consequently impact nitrous oxide (N₂O) emissions from paddy fields. The objective of this study was to investigate the response of N₂O emissions from paddy fields to different irrigation and nitrogen treatments and evaluate how the changes in soil microbial population influence N₂O emissions from paddy fields in South China under different irrigation and nitrogen management. Field experiments of late rice and early rice were conducted with three irrigation methods, i.e. conventional irrigation (CIR), “thin-shallow-wet-dry” irrigation (TIR) and alternate wetting and drying irrigation (DIR), and two nitrogen treatments, including 100% urea-N (FM1) and 50% urea-N and 50% pig manure-N (FM2). Results show that total N₂O emissions of both seasons in DIR were 3.2–3.5 times higher than those in CIR, and the total N₂O emissions of both seasons in FM2 were 1.7 times higher than those in FM1 under DIR. Compared to CIR, TIR augmented the population of nitrifying bacteria (NB) but decreased the population of denitrifying bacteria (DNB) at the milky stage, and DIR enhanced the communities of ammonia-oxidizing bacteria and NB but reduced the DNB. Correlation analysis shows that N₂O emission flux had a significantly positive correlation with soil NB (r= 0.541** and 0.542** for late and early rice fields). Thus, CRI had lower cumulative N₂O emission under FM1, and the changes in the nitrifying bacteria community greatly influenced N₂O emissions from paddy fields under different irrigation and nitrogen strategies.     

Responses of soil nitrous oxide production and abundances and composition of associated microbial communities to nitrogen and water amendment

Soil moisture and nitrogen (N) are two important factors influencing N₂O emissions and the growth of microorganisms. Here, we carried out a microcosm experiment to evaluate effects of soil moisture level and N fertilizer type on N₂O emissions and abundances and composition of associated microbial communities in the two typical arable soils. The abundances and community composition of functional microbes involved in nitrification and denitrification were determined via quantitative PCR (qPCR) and terminal restriction length fragment polymorphism (T-RFLP), respectively. Results showed that N₂O production was higher at 90% water-filled pore (WFPS) than at 50% WFPS. The N₂O emissions in the two soils amended with ammonium were higher than those amended with nitrate, especially at relatively high moisture level. In both soils, increased soil moisture stimulated the growth of ammonia-oxidizing bacteria (AOB) and nitrite reducer (nirK). Ammonium fertilizer treatment increased the population size of AOB and nirK genes in the alluvial soil, while reduced the abundances of ammonia-oxidizing archaea (AOA) and denitrifiers (nirK and nosZ) in the red soil. Nitrate addition had a negative effect on AOA abundance in the red soil. Total N₂O emissions were positively correlated to AOB abundance, but not to other functional genes in the two soils. Changed soil moisture significantly affected AOA rather than AOB community composition in both soils. The way and extent of N fertilizers impacted on nitrifier and denitrifier community composition varied with N form and soil type. These results indicate that N₂O emissions and the succession of nitrifying and denitrifying communities are selectively affected by soil moisture and N fertilizer form in the two contrasting types of soil.     

Earthworm regulation of nitrogen pools and dynamics and marker genes of nitrogen cycling: A meta-analysis

Earthworms, as the ecosystem engineers, both directly and indirectly affect the nitrogen(N) cycle. We aimed to provide a quantitative assessment of the contribution of earthworms to the terrestrial ecosystem N cycle using meta-analysis of 130 publications selected. The natural logarithm of the response ratio(lnRR) was used to indicate the effect size of earthworms on N dynamic variables. The results showed that earthworms significantly affected soil N-cycling microorganisms, including the amoA gene abundance of soil ammonia-oxidizing bacteria(AOB), and significantly promoted soil N cycle processes,including denitrification, mineralization, and plant assimilation. The effects of earthworms on the N cycle were experimental design dependent and affected by factors such as the functional group of earthworm and residue input. The presence of the anecic earthworms decreased the rates of mineralization and nitrification, and increased nitrification and denitrification responses were more pronounced in the presence of the endogeic earthworms than that of the other two functional groups of earthworms. In addition, residue input enhanced the effects of earthworms on the N cycle. The effects of earthworms on nitrous oxide(N₂ O) emission increased when residues were added. These findings indicate that residue input and introducing suitable functional groups of earthworms into the field can lead to N sustainability without increasing N2 O emission. This meta-analysis also provides systematic evidence for the positive effects of earthworms on the plant N pool, N availability(soil ammonium(NH₄⁺) content), and soil microbial biomass N content, showing the potential to alter ecosystem functions and services in relation to N cycling.     

Impact of Long-Term Application of Fertilizers on N2O and NO Production Potential in an Intensively Cultivated Sandy Loam Soil

Literature reports on N₂O and NO emissions from organic and mineral agricultural soil amended with N-containing fertilizers have reached contradictory conclusions. To understand the influence of organic manure (OM) and chemical fertilizer application on N₂O and NO emissions, we conducted laboratory incubation experiments on an agricultural sandy loam soil exposed to different long-term fertilization practices. The fertilizer treatments were initiated in 1989 at the Fengqiu State Key Agro-ecological Experimental Station and included a control without fertilizer (CK), OM, mineral NPK fertilizer (NPK), mineral NP fertilizer (NP), and mineral NK fertilizer (NK). The proportion of N emitted as NO and N₂O varied considerably among fertilizer treatments, ranging from 0.83% to 2.50% as NO and from 0.08% to 0.36% as N₂O. Cumulative NO emission was highest in the CK treatment after NH ₄ ⁺ -N was added at a rate of 200 mg N kg^?1 soil during the 612-h incubation period, whereas the long-term application of fertilizers significantly reduced NO emission by 54–67%. In contrast, the long-term application of NPK fertilizer and OM significantly enhanced N₂O emission by 95.6% and 253%, respectively, compared to CK conditions. The addition of NP fertilizer (no K) significantly reduced N₂O emission by 25.5%, whereas applications of NK fertilizer (no P) had no effect. The difference among the N-fertilized treatments was due probably to discrepancies in the N₂O production potential of the dominant ammonia-oxidizing bacteria (AOB) species rather than AOB abundance. The ratio of NO/N₂O was approximately 24 in the CK treatment, significantly higher than those in the N-fertilized treatments (3–11), and it decreased with increasing N₂O production potential in N-fertilized treatments. Our data suggests that the shift in the dominant AOB species might produce reciprocal change in cumulative NO and N₂O emissions.     

Field-scale and laboratory study of factors affecting N2O emissions from a rye stubble field on sandy loam soil

Emission of N₂O from cultivated and fertilised soils may contribute significantly to the total global N₂O emission. This study included laboratory and field investigations of the N₂O production from a dry stubble field as influenced by addition of water, nitrogen and glucose. N₂O fluxes were measured using a closed-chamber technique, and the O₂ content in the soil was measured using soil probes. Results from a laboratory soil core technique were correlated to the relative N₂O emission observed in the field. When the soil water content in the field increased from 14% to 60% water-filled pore space, the N₂O emission increased from non-significant to a constant emission of 30 μg N m^–2 h^–1. At this soil water content the production of N₂O was limited by the availability of nitrogen and carbon. Application of nitrogen at soil temperatures of 13 and 21°C in a pre-wetted soil increased the N₂O emission 3.1- and 3.7-fold, respectively, whereas nitrogen plus carbon application increased the N₂O emission 13.3- and 7.3-fold, respectively. In both treatments the N₂O emission rates were affected by fluctuations in soil temperature and O₂ content. The results indicate that even in a soil producing very little N₂O under dry conditions, the soil microbial community maintains a potential to produce N₂O when favourable conditions occur in terms of availability of water, nitrogen and carbon. Received: 21 October 1996     

Nitrification, ammonia-oxidizing communities, and N2O and CH4 fluxes in an imperfectly drained agricultural field fertilized with coated urea with and without dicyandiamide

Agricultural soil is a major source of nitrous oxide (N₂O), and the application of nitrogen and soil drainage are important factors affecting N₂O emissions. This study tested the use of polymer-coated urea (PCU) and polymer-coated urea with the nitrification inhibitor dicyandiamide (PCUD) as potential mitigation options for N₂O emissions in an imperfectly drained, upland converted paddy field. Fluxes of N₂O and methane (CH₄), ammonia oxidation potential, and ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) abundances were monitored after the application of PCU, PCUD, and urea to upland soil. The results showed that urea application increased the ammonia oxidation potential and AOB and AOA abundances; however, the increase rate of AOB (4.6 times) was much greater than that of AOA (1.8 times). These results suggested that both AOB and AOA contributed to ammonia oxidation after fertilizer application, but the response of AOB was greater than AOA. Although PCU and PCUD had lower ammonia oxidation potential compared to urea treatment, they were not effective in reducing N₂O emissions. Large episodic N₂O emissions (up to 1.59 kg N ha^?1 day^?1) were observed following heavy rainfall 2 months after basal fertilizer application. The episodic N₂O emissions accounted for 55–80 % of total N₂O emissions over the entire monitoring period. The episodic N₂O emissions following heavy rainfall would be a major source of N₂O in poorly drained agricultural fields. Cumulative CH₄ emissions ranged from ?0.017 to ?0.07 kg CH₄ ha^?1, and fertilizer and nitrification inhibitor application did not affect CH₄ oxidation.     

施肥方式对紫色土农田生态系统N2O和NO排放的影响

依托紫色土施肥方式与养分循环长期试验平台(2002年—),采用静态箱-气相色谱法开展紫色土冬小麦-夏玉米轮作周期(2013年10月至2014年10月)农田生态系统N_2O和NO排放的野外原位观测试验。长期施肥方式包括单施氮肥(N)、传统猪厩肥(OM)、常规氮磷钾肥(NPK)、猪厩肥配施氮磷钾肥(OMNPK)和秸秆还田配施氮磷钾肥(RSDNPK)等5种,氮肥用量相同[小麦季130 kg(N)×hm~(-2),玉米季150 kg(N)×hm~(-2)],不施肥对照(CK)用于计算排放系数,对比不同施肥方式对紫色土典型农田生态系统土壤N_2O和NO排放的影响,以期探寻紫色土农田生态系统N_2O和NO协同减排的施肥方式。结果表明,所有施肥方式下紫色土N_2O和NO排放速率波动幅度大,且均在施肥初期出现峰值;强降雨激发N_2O排放,但对NO排放无明显影响。在整个小麦-玉米轮作周期,N、OM、NPK、OMNPK和RSDNPK处理的N_2O年累积排放量分别为1.40 kg(N)×hm~(-2)、4.60 kg(N)×hm~(-2)、0.95 kg(N)×hm~(-2)、2.16kg(N)×hm~(-2)和1.41 kg(N)×hm~(-2),排放系数分别为0.41%、1.56%、0.25%、0.69%、0.42%;NO累积排放量分别为0.57 kg(N)×hm~(-2)、0.40 kg(N)×hm~(-2)、0.39 kg(N)×hm~(-2)、0.46 kg(N)×hm~(-2)和0.17 kg(N)×hm~(-2),排放系数分别为0.21%、0.15%、0.15%、0.17%、0.07%。施肥方式对紫色土N_2O和NO累积排放量具有显著影响(P0.05),与NPK处理比较,OM和OMNPK处理的N_2O排放分别增加384%和127%,同时NO排放分别增加3%和18%;RSDNPK处理的NO排放减少56%。表明长期施用猪厩肥显著增加N_2O和NO排放,而秸秆还田有效减少NO排放。研究表明,土壤温度和水分条件均显著影响小麦季N_2O和NO排放(P0.01),对玉米季N_2O和NO排放没有显著影响(P0.05),土壤无机氮含量则是在小麦-玉米轮作期N_2O和NO排放的主要限制因子(P0.01)。全量秸秆还田与化肥配合施用是紫色土农田生态系统N_2O和NO协同减排的优化施肥方式。     

Effect of calcareous and siliceous amendments on N2O emissions of a grassland soil

Liming of acidic agricultural soils has been proposed as a strategy to mitigate nitrous oxide (N₂O) emissions, as increased soil pH reduces the N₂O/N₂ product ratio of denitrification. The capacity of different calcareous (calcite and dolomite) and siliceous minerals to increase soil pH and reduce N₂O emissions was assessed in a 2-year grassland field experiment. An associated pot experiment was conducted using homogenized field soils for controlling spatial soil variability. Nitrous oxide emissions were highly episodic with emission peaks in response to freezing–thawing and application of NPK fertilizer. Liming with dolomite caused a pH increase from 5.1 to 6.2 and reduced N₂O emissions by 30% and 60% after application of NPK fertilizer and freezing–thawing events, respectively. Over the course of the 2-year field trial, N₂O emissions were significantly lower in dolomite-limed than non-limed soil (p < .05), although this effect was variable over time. Unexpectedly, no significant reduction of N₂O emission was found in the calcite treatment, despite the largest pH increase in all tested minerals. We tentatively attribute this to increased N₂O production by overall increase in nitrogen turnover rates (both nitrification and denitrification) following rapid pH increase in the first year after liming. Siliceous materials showed little pH effect and had no significant effect on N₂O emissions probably because of their lower buffering capacity and lower cation content. In the pot experiment using soils taken from the field plots 3 years after liming and exposing them to natural freezing–thawing, both calcite (p < .01) and dolomite (p < .05) significantly reduced cumulative N₂O emission by 50% and 30%, respectively, relative to the non-limed control. These results demonstrate that the overall effect of liming is to reduce N₂O emission, although high lime doses may lead to a transiently enhanced emission.     

生物质炭添加对不同pH紫色土硝化作用及N2O排放的影响

生物质炭施用可能对土壤中氮素硝化过程和N₂O排放产生影响。本研究通过室内培养试验,研究铵态氮肥与玉米秸秆生物质炭施用量(0、1%、2%、5%、10%,m/m)对酸性(pH 5.10)和石灰性(pH 8.15)紫色土氮素硝化率、净硝化速率及N₂O排放特征的影响。结果表明:①酸性和石灰性紫色土生物质炭处理平均净硝化速率相比对照分别降低了33.7%～93.7%和7.5%～40.9%,生物质炭添加抑制了酸性和石灰性紫色土硝化作用,在酸性紫色土中生物质炭对硝化作用的抑制作用随施用量的增加而增强,在石灰性紫色土中无明显规律。②与对照相比,酸性紫色土N₂O累计排放量在1%生物质炭和2%生物质炭处理下降幅分别为15.9%和27.7%,在5%和10%生物质炭处理下增幅分别为60.1%和93.2%;石灰性紫色土生物质炭各处理N₂O累积排放量均显著高于对照。③综合考虑,在酸性紫色土中1%、2%生物质炭施用对硝化作用抑制和N₂O减排综合效果最好,但在石灰性紫色土中无明显抑制和减排效果。     

林分类型和氮添加对亚热带森林土壤氧化亚氮排放的影响

为揭示亚热带森林土壤N₂O排放对林分类型和氮添加的响应特征,选取位于福建省三明市的中亚热带米槠次生林、杉木人工林和马尾松人工林土壤为研究对象,分别设置无氮添加(N0 mg/kg)、低氮添加(N10 mg/kg)、中氮添加(N25 mg/kg)和高氮添加(N50 mg/kg)4个氮添加水平,进行微宇宙培养试验,测定土壤N₂O排放。结果表明：与无氮添加处理相比,氮添加整体上降低3种林分土壤pH,增加土壤NH₄⁺-N和NO₃^--N含量。无氮添加处理中杉木人工林和马尾松人工林土壤N₂O累积排放量分别为9.67和9.62 mg/kg,显著高于米槠次生林土壤N₂O累积排放量6.81 mg/kg。低氮添加处理中杉木人工林和马尾松人工林土壤N₂O累积排放量显著高于米槠次生林。但在中氮和高氮添加处理中,3种林分土壤N₂O累积排放量均无显著性差异。不同氮添加处理均促进3种林分土壤N     

丛枝菌根真菌调控土壤氧化亚氮排放的机制

氮素是陆地生态系统初级生产力的主要限制因子,自Haber-Bosch反应以来,氮肥的生产和施用极大地提高了粮食产量.然而过量施用氮肥导致氮肥利用率低,并造成了严重的环境污染,包括氮沉降、硝态氮淋洗以及N2O排放等.微生物直接参与土壤氮素循环,固氮微生物、氨氧化和反硝化微生物分别在土壤固氮、铵态氮转化和硝态氮转化过程中起...     

水稻根际和周围土壤中微生物功能基因丰度与碳、氮状况及其通量之间的关系

Rapid nitrogen（N） transformations and losses occur in the rice rhizosphere through root uptake and microbial activities. However,the relationships between rice roots and rhizosphere microbes for N utilization are still unclear. We analyzed different N forms（NH＋4,NO-3, and dissolved organic N）, microbial biomass N and C, dissolved organic C, CH4 and N2O emissions, and abundance of microbial functional genes in both rhizosphere and bulk soils after 37-d rice growth in a greenhouse pot experiment. Results showed that the dissolved organic C was significantly higher in the rhizosphere soil than in the non-rhizosphere bulk soil, but microbial biomass C showed no significant difference. The concentrations of NH＋4, dissolved organic N, and microbial biomass N in the rhizosphere soil were significantly lower than those of the bulk soil, whereas NO-3in the rhizosphere soil was comparable to that in the bulk soil. The CH4 and N2O fluxes from the rhizosphere soil were much higher than those from the bulk soil. Real-time polymerase chain reaction analysis showed that the abundance of seven selected genes, bacterial and archaeal 16 S rRNA genes, amoA genes of ammonia-oxidizing archaea and ammonia-oxidizing bacteria, nosZ gene, mcrA gene, and pmoA gene, was lower in the rhizosphere soil than in the bulk soil, which is contrary to the results of previous studies. The lower concentration of N in the rhizosphere soil indicated that the competition for N in the rhizosphere soil was very strong, thus having a negative effect on the numbers of microbes. We concluded that when N was limiting, the growth of rhizosphere microorganisms depended on their competitive abilities with rice roots for N.     

肥料添加剂降低N2O排放的效果与机理

如何降低氮肥施入农田后的N2O排放,实现氮肥增产效应的同时降低其对环境的负面影响是全球集约化农业生产中重要的科学问题,氮肥添加剂是有效途径之一。本研究采用室内静态培养法,在调节土壤水分含量和温度等环境因素的条件下,研究不同肥料添加剂对华北平原典型农田土壤N2O排放的影响及其机制。结果表明,N2O排放通量的峰值大约出现在施氮后的第24 d,肥料混施较肥料表施的出峰时间提前。与单施尿素处理相比,添加硝化抑制剂DMPP或DCD能分别降低N2O排放总量99.2%和97.1%; 添加硫酸铜对N2O排放的抑制作用不显著; 添加秸秆会增加N2O排放总量60.7%,而在添加秸秆的土壤中施加硝化抑制剂DMPP能够显著降低N2O排放量至无肥对照水平。说明华北平原农田土壤中N2O的产生主要是由硝化作用驱动,同时也可看出,添加硝化抑制剂是N2O减排的有效措施。     

Tillage system affects fertilizer-induced nitrous oxide emissions

Since the development of effective N₂O mitigation options is a key challenge for future agricultural practice, we studied the interactive effect of tillage systems on fertilizer-derived N₂O emissions and the abundance of microbial communities involved in N₂O production and reduction. Soil samples from 0–10 cm and 10–20 cm depth of reduced tillage and ploughed plots were incubated with dairy slurry (SL) and manure compost (MC) in comparison with calcium ammonium nitrate (CAN) and an unfertilized control (ZERO) for 42 days. N₂O and CO₂ fluxes, ammonium, nitrate, dissolved organic C, and functional gene abundances (16S rRNA gene, nirK, nirS, nosZ, bacterial and archaeal amoA) were regularly monitored. Averaged across all soil samples, N₂O emissions decreased in the order CAN and SL (CAN?=?748.8?±?206.3, SL?=?489.4?±?107.2 μg kg^?1) followed by MC (284.2?±?67.3 μg kg^?1) and ZERO (29.1?±?5.9 μg kg^?1). Highest cumulative N₂O emissions were found in 10–20 cm of the reduced tilled soil in CAN and SL. N₂O fluxes were assigned to ammonium as source in CAN and SL and correlated positively to bacterial amoA abundances. Additionally, nosZ abundances correlated negatively to N₂O fluxes in the organic fertilizer treatments. Soils showed a gradient in soil organic C, 16S rRNA, nirK, and nosZ with greater amounts in the 0–10 than 10–20 cm layer. Abundances of bacterial and archaeal amoA were higher in reduced tilled soil compared to ploughed soils. The study highlights that tillage system induced biophysicochemical stratification impacts net N₂O emissions within the soil profile according to N and C species added during fertilization.     

除草剂对不同种植年限柑橘园土壤氮转化过程及温室气体排放的影响

为探讨除草剂施用对柑橘园土壤氮转化及温室气体排放的影响,在实验室培养条件下,研究了0年(林地)、种植10年和30年的柑橘园土壤中分别添加除草剂草甘膦和丁草胺后,尿素态氮含量、硝化和反硝化作用以及温室气体排放的变化。研究结果表明,橘园土壤中尿素第1 d的水解率、氮肥硝化率、反硝化作用损失总量以及N_2O和CO_2排放量显著高于林地土壤(P0.05)。与10年橘园土壤相比,30年橘园土壤显著增加了尿素的水解速率、氮肥硝化率和CO_2排放量(P0.05),但二者的反硝化损失量没有显著差异。施用草甘膦和丁草胺都显著促进了林地土壤的尿素水解(P0.05),第1 d尿素态氮含量分别降低11.20%和12.43%;但对3种土壤氮肥的硝化率均没有明显影响。施用丁草胺显著降低了林地土壤的CO_2排放量(P0.05),对两种橘园土壤的CO_2排放没有明显影响,但明显增加了两种橘园土壤的N_2O排放总量(P0.05),分别比不施除草剂增加56.27%和85.41%;施用草甘膦对3种土壤的N_2O和CO_2排放均没有明显影响。可见,草甘膦和丁草胺的施用不会对柑橘园土壤的氮转化过程产生影响,但丁草胺显著增加了柑橘园土壤的N_2O排放。     

Differences in CO2 and N2O emission rates following crop residue incorporation with or without field burning: A case study of adzuki bean residue and wheat straw

In the context of sustainable soil-quality management and mitigating global warming, the impacts of incorporating raw or field-burned adzuki bean (Vigna angularis (Willd.) Ohwi & Ohashi) and wheat (Triticum aestivum L.) straw residues on carbon dioxide (CO₂) and nitrous oxide (N₂O) emission rates from soil were assessed in an Andosol field in northern Japan. Losses of carbon (C) and nitrogen (N) in residue biomass during field burning were much greater from adzuki bean residue (98.6% of C and 98.1% of N) than from wheat straw (85.3% and 75.3%, respectively). Although we noted considerable inputs of carbon (499 ± 119 kg C ha^–1) and nitrogen (5.97 ± 0.76 kg N ha^–1) from burned wheat straw into the soil, neither CO₂ nor N₂O emission rates from soil (over 210 d) increased significantly after the incorporation of field-burned wheat straw. Thus, the field-burned wheat straw contained organic carbon fractions that were more resistant to decomposition in soil in comparison with the unburned wheat straw. Our results and previously reported rates of CO₂, methane (CH₄) and N₂O emission during wheat straw burning showed that CO₂-equivalent greenhouse gas emissions under raw residue incorporation were similar to or slightly higher than those under burned residue incorporation when emission rates were assessed during residue burning and after subsequent soil incorporation.